IDE ATA/133 is a newer specification for the interface between your computer and the hard drive. Most people who are adopting IDE ATA/133 are doing so to support the newest, high-capacity hard drives larger than 137GB in size.
IDE RAID is a method for combining multiple IDE drives into a high-performance and/or redundant volume. For example, IDE RAID can be used to create a mirror that automatically copies all data from one drive to the second drive. Then, if one of the drives fails, the remaining drive will keep the computer running and the data safe.
IDE ATA/133 and IDE RAID aren't mutually exclusive. There are IDE RAID cards that support the IDE ATA/133 standard. To answer your second question, older drives will work fine with either type of card.
This was first published in September 2002